Inflammation of the root of a tooth is clinically known as periapical infection, which usually does not heal on its own and requires root canal treatment at a hospital dentistry department. The most common cause of periapical inflammation is the spread of infected material in the root canal, through the apical foramen of the root, into the periapical tissues, with the ultimate cause of infection being a bacterial infection. Bacterial infection cannot achieve self-healing without systematic treatment because its main source of bacteria is the necrotic pulp tissue within the root. If the infected necrotic pulp tissue is not removed, even if the acute symptoms outside the periapical area are eliminated by taking anti-inflammatory drugs, the source of infection still exists and the bacteria will continue to proliferate and develop, and periapical periodontitis will form again. Therefore, periapical infection should be treated early with root canal therapy, and only after cutting off the source of infection can the periapical tissues be cured.